Recommendations for Nomenclature and Definition Of Cell Products Intended for Human Cardiovascular Use

Exogenous cell-based therapy has emerged as a promising new strategy to facilitate repair of hearts damaged by acute or chronic injury. However, the field of cell-based therapy is handicapped by the lack of standardized definitions and terminology, making comparisons across studies challenging. Even the term "stem cell therapy" is misleading because only a small percentage of cells derived from adult bone marrow, peripheral blood, or adipose tissue meets the accepted hematopoietic or developmental definition of stem cells. Furthermore, cells (stem or otherwise) are dynamic biological products, meaning that their surface marker expression, phenotypic and functional characteristics, and the products they secrete in response to their microenvironment can change. It is also important to point out that most surface markers are seldom specific for a cell type. In this article, we discuss the lack of consistency in the descriptive terminology used in cell-based therapies and offer guidelines aimed at standardizing nomenclature and definitions to improve communication among investigators and the general public.

A Phase II study of autologous mesenchymal stromal cells and c-kit positive cardiac cells, alone or in combination, in patients with ischaemic heart failure: the CCTRN CONCERT-HF trial

AIMS

CONCERT-HF is an NHLBI-sponsored, double-blind, placebo-controlled, Phase II trial designed to determine whether treatment with autologous bone marrow-derived mesenchymal stromal cells (MSCs) and c-kit positive cardiac cells (CPCs), given alone or in combination, is feasible, safe, and beneficial in patients with heart failure (HF) caused by ischaemic cardiomyopathy.

METHODS AND RESULTS

Patients were randomized (1:1:1:1) to transendocardial injection of MSCs combined with CPCs, MSCs alone, CPCs alone, or placebo, and followed for 12 months. Seven centres enrolled 125 participants with left ventricular ejection fraction of 28.6 ± 6.1% and scar size 19.4 ± 5.8%, in New York Heart Association class II or III. The proportion of major adverse cardiac events (MACE) was significantly decreased by CPCs alone (-22% vs. placebo, P = 0.043). Quality of life (Minnesota Living with Heart Failure Questionnaire score) was significantly improved by MSCs alone (P = 0.050) and MSCs + CPCs (P = 0.023) vs. placebo. Left ventricular ejection fraction, left ventricular volumes, scar size, 6-min walking distance, and peak oxygen consumption did not differ significantly among groups.

CONCLUSIONS

This is the first multicentre trial assessing CPCs and a combination of two cell types from different tissues in HF patients. The results show that treatment is safe and feasible. Even with maximal guideline-directed therapy, both CPCs and MSCs were associated with improved clinical outcomes (MACE and quality of life, respectively) in ischaemic HF without affecting left ventricular function or structure, suggesting possible systemic or paracrine cellular mechanisms. Combining MSCs with CPCs was associated with improvement in both these outcomes. These results suggest potential important beneficial effects of CPCs and MSCs and support further investigation in HF patients.

Allogeneic Mesenchymal Cell Therapy in Anthracycline-Induced Cardiomyopathy Heart Failure Patients: The CCTRN SENECA Trial

BACKGROUND

Anthracycline-induced cardiomyopathy (AIC) may be irreversible with a poor prognosis, disproportionately affecting women and young adults. Administration of allogeneic bone marrow-derived mesenchymal stromal cells (allo-MSCs) is a promising approach to heart failure (HF) treatment.

OBJECTIVES

SENECA (Stem Cell Injection in Cancer Survivors) was a phase 1 study of allo-MSCs in AIC.

METHODS

Cancer survivors with chronic AIC (mean age 56.6 years; 68% women; NT-proBNP 1,426 pg/ml; 6 enrolled in an open-label, lead-in phase and 31 subjects randomized 1:1) received 1 × 10⁸ allo-MSCs or vehicle transendocardially. Primary objectives were safety and feasibility. Secondary efficacy measures included cardiac function and structure measured by cardiac magnetic resonance imaging (CMR), functional capacity, quality of life (Minnesota Living with Heart Failure Questionnaire), and biomarkers.

RESULTS

A total of 97% of subjects underwent successful study product injections; all allo-MSC-assigned subjects received the target dose of cells. Follow-up visits were well-attended (92%) with successful collection of endpoints in 94% at the 1-year visit. Although 58% of subjects had non-CMR compatible devices, CMR endpoints were successfully collected in 84% of subjects imaged at 1 year. No new tumors were reported. There were no significant differences between allo-MSC and vehicle groups with regard to clinical outcomes. Secondary measures included 6-min walk test (p = 0.056) and Minnesota Living with Heart Failure Questionnaire score (p = 0.048), which tended to favor the allo-MSC group.

CONCLUSIONS

In this first-in-human study of cell therapy in patients with AIC, transendocardial administration of allo-MSCs appears safe and feasible, and CMR was successfully performed in the majority of the HF patients with devices. This study lays the groundwork for phase 2 trials aimed at assessing efficacy of cell therapy in patients with AIC.

Rationale and Design of the SENECA (StEm cell iNjECtion in cAncer survivors) Trial

OBJECTIVES

SENECA (StEm cell iNjECtion in cAncer survivors) is a phase I, randomized, double-blind, placebo-controlled study to evaluate the safety and feasibility of delivering allogeneic mesenchymal stromal cells (allo-MSCs) transendocardially in subjects with anthracycline-induced cardiomyopathy (AIC).

BACKGROUND

AIC is an incurable and often fatal syndrome, with a prognosis worse than that of ischemic or nonischemic cardiomyopathy. Recently, cell therapy with MSCs has emerged as a promising new approach to repair damaged myocardium.

METHODS

The study population is 36 cancer survivors with a diagnosis of AIC, left ventricular (LV) ejection fraction ≤40%, and symptoms of heart failure (NYHA class II-III) on optimally-tolerated medical therapy. Subjects must be clinically free of cancer for at least two years with a ≤ 30% estimated five-year risk of recurrence. The first six subjects participated in an open-label, lead-in phase and received 100 million allo-MSCs; the remaining 30 will be randomized 1:1 to receive allo-MSCs or vehicle via 20 transendocardial injections. Efficacy measures (obtained at baseline, 6 months, and 12 months) include MRI evaluation of LV function, LV volumes, fibrosis, and scar burden; assessment of exercise tolerance (six-minute walk test) and quality of life (Minnesota Living with Heart Failure Questionnaire); clinical outcomes (MACE and cumulative days alive and out of hospital); and biomarkers of heart failure (NT-proBNP).

CONCLUSIONS

This is the first clinical trial using direct cardiac injection of cells for the treatment of AIC. If administration of allo-MSCs is found feasible and safe, SENECA will pave the way for larger phase II/III studies with therapeutic efficacy as the primary outcome.

Rationale and Design of the CONCERT-HF Trial (Combination of Mesenchymal and c-kit+ Cardiac Stem Cells As Regenerative Therapy for Heart Failure)

RATIONALE

Autologous bone marrow mesenchymal stem cells (MSCs) and c-kit⁺ cardiac progenitor cells (CPCs) are 2 promising cell types being evaluated for patients with heart failure (HF) secondary to ischemic cardiomyopathy. No information is available in humans about the relative efficacy of MSCs and CPCs and whether their combination is more efficacious than either cell type alone.

OBJECTIVE

CONCERT-HF (Combination of Mesenchymal and c-kit⁺ Cardiac Stem Cells As Regenerative Therapy for Heart Failure) is a phase II trial aimed at elucidating these issues by assessing the feasibility, safety, and efficacy of transendocardial administration of autologous MSCs and CPCs, alone and in combination, in patients with HF caused by chronic ischemic cardiomyopathy (coronary artery disease and old myocardial infarction).

METHODS AND RESULTS

Using a randomized, double-blinded, placebo-controlled, multicenter, multitreatment, and adaptive design, CONCERT-HF examines whether administration of MSCs alone, CPCs alone, or MSCs+CPCs in this population alleviates left ventricular remodeling and dysfunction, reduces scar size, improves quality of life, or augments functional capacity. The 4-arm design enables comparisons of MSCs alone with CPCs alone and with their combination. CONCERT-HF consists of 162 patients, 18 in a safety lead-in phase (stage 1) and 144 in the main trial (stage 2). Stage 1 is complete, and stage 2 is currently randomizing patients from 7 centers across the United States.

CONCLUSIONS

CONCERT-HF will provide important insights into the potential therapeutic utility of MSCs and CPCs, given alone and in combination, for patients with HF secondary to ischemic cardiomyopathy.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02501811.

TIME Trial: Effect of Timing of Stem Cell Delivery Following ST-Elevation Myocardial Infarction on the Recovery of Global and Regional Left Ventricular Function: Final 2-Year Analysis

RATIONALE

The TIME trial (Timing in Myocardial Infarction Evaluation) was the first cell therapy trial sufficiently powered to determine if timing of cell delivery after ST-segment-elevation myocardial infarction affects recovery of left ventricular (LV) function.

OBJECTIVE

To report the 2-year clinical and cardiac magnetic resonance imaging results and their modification by microvascular obstruction.

METHODS AND RESULTS

TIME was a randomized, double-blind, placebo-controlled trial comparing 150 million bone marrow mononuclear cells versus placebo in 120 patients with anterior ST-segment-elevation myocardial infarctions resulting in LV dysfunction. Primary end points included changes in global (LV ejection fraction) and regional (infarct and border zone) function. Secondary end points included changes in LV volumes, infarct size, and major adverse cardiac events. Here, we analyzed the continued trajectory of these measures out to 2 years and the influence of microvascular obstruction present at baseline on these long-term outcomes. At 2 years (n=85), LV ejection fraction was similar in the bone marrow mononuclear cells (48.7%) and placebo groups (51.6%) with no difference in regional LV function. Infarct size and LV mass decreased ≥30% in each group at 6 months and declined gradually to 2 years. LV volumes increased ≈10% at 6 months and remained stable to 2 years. Microvascular obstruction was present in 48 patients at baseline and was associated with significantly larger infarct size (56.5 versus 36.2 g), greater adverse LV remodeling, and marked reduction in LV ejection fraction recovery (0.2% versus 6.2%).

CONCLUSIONS

In one of the longest serial cardiac magnetic resonance imaging analyses of patients with large anterior ST-segment-elevation myocardial infarctions, bone marrow mononuclear cells administration did not improve recovery of LV function over 2 years. Microvascular obstruction was associated with reduced recovery of LV function, greater adverse LV remodeling, and more device implantations. The use of cardiac magnetic resonance imaging leads to greater dropout of patients over time because of device implantation in patients with more severe LV dysfunction resulting in overestimation of clinical stability of the cohort.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00684021.

Evaluation of Cell Therapy on Exercise Performance and Limb Perfusion in Peripheral Artery Disease: The CCTRN PACE Trial (Patients With Intermittent Claudication Injected With ALDH Bright Cells)

BACKGROUND

Atherosclerotic peripheral artery disease affects 8% to 12% of Americans >65 years of age and is associated with a major decline in functional status, increased myocardial infarction and stroke rates, and increased risk of ischemic amputation. Current treatment strategies for claudication have limitations. PACE (Patients With Intermittent Claudication Injected With ALDH Bright Cells) is a National Heart, Lung, and Blood Institute-sponsored, randomized, double-blind, placebo-controlled, phase 2 exploratory clinical trial designed to assess the safety and efficacy of autologous bone marrow-derived aldehyde dehydrogenase bright (ALDHbr) cells in patients with peripheral artery disease and to explore associated claudication physiological mechanisms.

METHODS

All participants, randomized 1:1 to receive ALDHbr cells or placebo, underwent bone marrow aspiration and isolation of ALDHbr cells, followed by 10 injections into the thigh and calf of the index leg. The coprimary end points were change from baseline to 6 months in peak walking time (PWT), collateral count, peak hyperemic popliteal flow, and capillary perfusion measured by magnetic resonance imaging, as well as safety.

RESULTS

A total of 82 patients with claudication and infrainguinal peripheral artery disease were randomized at 9 sites, of whom 78 had analyzable data (57 male, 21 female patients; mean age, 66±9 years). The mean±SEM differences in the change over 6 months between study groups for PWT (0.9±0.8 minutes; 95% confidence interval [CI] -0.6 to 2.5; P=0.238), collateral count (0.9±0.6 arteries; 95% CI, -0.2 to 2.1; P=0.116), peak hyperemic popliteal flow (0.0±0.4 mL/s; 95% CI, -0.8 to 0.8; P=0.978), and capillary perfusion (-0.2±0.6%; 95% CI, -1.3 to 0.9; P=0.752) were not significant. In addition, there were no significant differences for the secondary end points, including quality-of-life measures. There were no adverse safety outcomes. Correlative relationships between magnetic resonance imaging measures and PWT were not significant. A post hoc exploratory analysis suggested that ALDHbr cell administration might be associated with an increase in the number of collateral arteries (1.5±0.7; 95% CI, 0.1-2.9; P=0.047) in participants with completely occluded femoral arteries.

CONCLUSIONS

ALDHbr cell administration did not improve PWT or magnetic resonance outcomes, and the changes in PWT were not associated with the anatomic or physiological magnetic resonance imaging end points. Future peripheral artery disease cell therapy investigational trial design may be informed by new anatomic and perfusion insights.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01774097.

Bone marrow cell characteristics associated with patient profile and cardiac performance outcomes in the LateTIME-Cardiovascular Cell Therapy Research Network (CCTRN) trial

BACKGROUND

Although several preclinical studies have shown that bone marrow cell (BMC) transplantation promotes cardiac recovery after myocardial infarction, clinical trials with unfractionated bone marrow have shown variable improvements in cardiac function.

METHODS

To determine whether in a population of post-myocardial infarction patients, functional recovery after BM transplant is associated with specific BMC subpopulation, we examined the association between BMCs with left ventricular (LV) function in the LateTIME-CCTRN trial.

RESULTS

In this population, we found that older individuals had higher numbers of BM CD133(+) and CD3(+) cells. Bone marrow from individuals with high body mass index had lower CD45(dim)/CD11b(dim) levels, whereas those with hypertension and higher C-reactive protein levels had higher numbers of CD133(+) cells. Smoking was associated with higher levels of CD133(+)/CD34(+)/VEGFR2(+) cells and lower levels of CD3(+) cells. Adjusted multivariate analysis indicated that CD11b(dim) cells were negatively associated with changes in LV ejection fraction and wall motion in both the infarct and border zones. Change in LV ejection fraction was positively associated with CD133(+), CD34(+), and CD45(+)/CXCR4(dim) cells as well as faster BMC growth rates in endothelial colony forming assays.

CONCLUSIONS

In the LateTIME population, BM composition varied with patient characteristics and treatment. Irrespective of cell therapy, recovery of LV function was greater in patients with greater BM abundance of CD133(+) and CD34(+) cells and worse in those with higher levels of CD11b(dim) cells. Bone marrow phenotype might predict clinical response before BMC therapy and administration of selected BM constituents could potentially improve outcomes of other future clinical trials.

Concise Review: Review and Perspective of Cell Dosage and Routes of Administration From Preclinical and Clinical Studies of Stem Cell Therapy for Heart Disease

An important stage in the development of any new therapeutic agent is establishment of the optimal dosage and route of administration. Inconsistent findings have been reported regarding the relationship between the cell dose and clinical benefit. The present study summarizes the data regarding the optimal cell dosage and route of administration from studies of stem cell therapy for heart disease and offers a perspective on future directions.

An important stage in the development of any new therapeutic agent is establishment of the optimal dosage and route of administration. This can be particularly challenging when the treatment is a biologic agent that might exert its therapeutic effects via complex or poorly understood mechanisms. Multiple preclinical and clinical studies have shown paradoxical results, with inconsistent findings regarding the relationship between the cell dose and clinical benefit. Such phenomena can, at least in part, be attributed to variations in cell dosing or concentration and the route of administration (ROA). Although clinical trials of cell-based therapy for cardiovascular disease began more than a decade ago, specification of the optimal dosage and ROA has not been established. The present review summarizes what has been learned regarding the optimal cell dosage and ROA from preclinical and clinical studies of stem cell therapy for heart disease and offers a perspective on future directions.

Significance

Preclinical and clinical studies on cell-based therapy for cardiovascular disease have shown inconsistent results, in part because of variations in study-specific dosages and/or routes of administration (ROA). Future preclinical studies and smaller clinical trials implementing cell-dose and ROA comparisons are warranted before proceeding to pivotal trials.

Identification of Bone Marrow Cell Subpopulations Associated With Improved Functional Outcomes in Patients With Chronic Left Ventricular Dysfunction: An Embedded Cohort Evaluation of the FOCUS-CCTRN Trial

In the current study, we sought to identify bone marrow-derived mononuclear cell (BM-MNC) subpopulations associated with a combined improvement in left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), and maximal oxygen consumption (VO₂ max) in patients with chronic ischemic cardiomyopathy 6 months after receiving transendocardial injections of autologous BM-MNCs or placebo. For this prospectively planned analysis, we conducted an embedded cohort study comprising 78 patients from the FOCUS-Cardiovascular Cell Therapy Research Network (CCTRN) trial. Baseline BM-MNC immunophenotypes and progenitor cell activity were determined by flow cytometry and colony-forming assays, respectively. Previously stable patients who demonstrated improvement in LVEF, LVESV, and VO₂ max during the 6-month course of the FOCUS-CCTRN study (group 1, n = 17) were compared to those who showed no change or worsened in one to three of these endpoints (group 2, n = 61) and to a subset of patients from group 2 who declined in all three functional endpoints (group 2A, n = 11). Group 1 had higher frequencies of B-cell and CXCR4⁺ BM-MNC subpopulations at study baseline than group 2 or 2A. Furthermore, patients in group 1 had fewer endothelial colony-forming cells and monocytes/macrophages in their bone marrow than those in group 2A. To our knowledge, this is the first study to show that in patients with ischemic cardiomyopathy, certain bone marrow-derived cell subsets are associated with improvement in LVEF, LVESV, and VO₂ max at 6 months. These results suggest that the presence of both progenitor and immune cell populations in the bone marrow may influence the natural history of chronic ischemic cardiomyopathy-even in stable patients. Thus, it may be important to consider the bone marrow composition and associated regenerative capacity of patients when assigning them to treatment groups and evaluating the results of cell therapy trials.

Bone marrow characteristics associated with changes in infarct size after STEMI: a biorepository evaluation from the CCTRN TIME trial

RATIONALE

Despite significant interest in bone marrow mononuclear cell (BMC) therapy for ischemic heart disease, current techniques have resulted in only modest benefits. However, selected patients have shown improvements after autologous BMC therapy, but the contributing factors are unclear.

OBJECTIVE

The purpose of this study was to identify BMC characteristics associated with a reduction in infarct size after ST-segment-elevation-myocardial infarction.

METHODS AND RESULTS

This prospective study comprised patients consecutively enrolled in the CCTRN TIME (Cardiovascular Cell Therapy Research Network Timing in Myocardial Infarction Evaluation) trial who agreed to have their BMCs stored and analyzed at the CCTRN Biorepository. Change in infarct size between baseline (3 days after percutaneous coronary intervention) and 6-month follow-up was measured by cardiac MRI. Infarct-size measurements and BMC phenotype and function data were obtained for 101 patients (mean age, 56.5 years; mean screening ejection fraction, 37%; mean baseline cardiac MRI ejection fraction, 45%). At 6 months, 75 patients (74.3%) showed a reduction in infarct size (mean change, -21.0±17.6%). Multiple regression analysis indicated that infarct size reduction was greater in patients who had a larger percentage of CD31(+) BMCs (P=0.046) and in those with faster BMC growth rates in colony-forming unit Hill and endothelial-colony forming cell functional assays (P=0.033 and P=0.032, respectively).

CONCLUSIONS

This study identified BMC characteristics associated with a better clinical outcome in patients with segment-elevation-myocardial infarction and highlighted the importance of endothelial precursor activity in regenerating infarcted myocardium. Furthermore, it suggests that for these patients with segment-elevation-myocardial infarction, myocardial repair was more dependent on baseline BMC characteristics than on whether the patient underwent intracoronary BMC transplantation.

CLINICAL TRIAL REGISTRATION INFORMATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00684021.

Rationale and design for PACE: patients with intermittent claudication injected with ALDH bright cells

Peripheral artery disease (PAD) is recognized as a public health issue because of its prevalence, functional limitations, and increased risk of systemic ischemic events. Current treatments for claudication, the primary symptom in patients with PAD, have limitations. Cells identified using cytosolic enzyme aldehyde dehydrogenase (ALDH) may benefit patients with severe PAD but has not been studied in patients with claudication. PACE is a randomized, double-blind, placebo-controlled clinical trial conducted by the Cardiovascular Cell Therapy Research Network to assess the safety and efficacy of autologous bone marrow-derived ALDH(br) cells delivered by direct intramuscular injections in 80 patients with symptom-limiting intermittent claudication. Eligible patients will have a significant stenosis or occlusion of infrainguinal arteries and a resting ankle-brachial index less than 0.90 and will be randomized 1:1 to cell or placebo treatment with a 1-year follow-up. The primary end points are the change in peak walking time and leg collateral arterial anatomy, calf muscle blood flow, and tissue perfusion as determined by magnetic resonance imaging at 6 months compared with baseline. The latter 3 measurements are new physiologic lower extremity tissue perfusion and PAD imaging-based end points that may help to quantify the biologic and mechanistic effects of cell therapy. This trial will collect important mechanistic and clinical information on the safety and efficacy of ALDH(br) cells in patients with claudication and provide valuable insight into the utility of advanced magnetic resonance imaging end points.

Detailed analysis of bone marrow from patients with ischemic heart disease and left ventricular dysfunction: BM CD34, CD11b, and clonogenic capacity as biomarkers for clinical outcomes

RATIONALE

Bone marrow (BM) cell therapy for ischemic heart disease (IHD) has shown mixed results. Before the full potency of BM cell therapy can be realized, it is essential to understand the BM niche after acute myocardial infarction (AMI).

OBJECTIVE

To study the BM composition in patients with IHD and severe left ventricular (LV) dysfunction.

METHODS AND RESULTS

BM from 280 patients with IHD and LV dysfunction were analyzed for cell subsets by flow cytometry and colony assays. BM CD34(+) cell percentage was decreased 7 days after AMI (mean of 1.9% versus 2.3%-2.7% in other cohorts; P<0.05). BM-derived endothelial colonies were significantly decreased (P<0.05). Increased BM CD11b(+) cells associated with worse LV ejection fraction (LVEF) after AMI (P<0.05). Increased BM CD34(+) percentage associated with greater improvement in LVEF (+9.9% versus +2.3%; P=0.03, for patients with AMI and +6.6% versus -0.02%; P=0.021 for patients with chronic IHD). In addition, decreased BM CD34(+) percentage in patients with chronic IHD correlated with decrement in LVEF (-2.9% versus +0.7%; P=0.0355).

CONCLUSIONS

In this study, we show a heterogeneous mixture of BM cell subsets, decreased endothelial colony capacity, a CD34+ cell nadir 7 days after AMI, a negative correlation between CD11b percentage and postinfarct LVEF, and positive correlation of CD34 percentage with change in LVEF after cell therapy. These results serve as a possible basis for the small clinical improvement seen in autologous BM cell therapy trials and support selection of potent cell subsets and reversal of comorbid BM impairment.

CLINICAL TRIAL REGISTRATIONS URL

http://www.clinicaltrials.gov. Unique identifiers: NCT00684021, NCT00684060, and NCT00824005.

Bone marrow mononuclear cell therapy for acute myocardial infarction: a perspective from the cardiovascular cell therapy research network

To understand the role of bone marrow mononuclear cells in the treatment of acute myocardial infarction, this overview offers a retrospective examination of strengths and limitations of 3 contemporaneous trials with attention to critical design features and provides an analysis of the combined data set and implications for future directions in cell therapy for acute myocardial infarction.

Bone marrow mononuclear cell therapy for acute myocardial infarction: a perspective from the cardiovascular cell therapy research network

To understand the role of bone marrow mononuclear cells in the treatment of acute myocardial infarction, this overview offers a retrospective examination of strengths and limitations of 3 contemporaneous trials with attention to critical design features and provides an analysis of the combined data set and implications for future directions in cell therapy for acute myocardial infarction.

Effect of the use and timing of bone marrow mononuclear cell delivery on left ventricular function after acute myocardial infarction: the TIME randomized trial

CONTEXT

While the delivery of cell therapy after ST-segment elevation myocardial infarction (STEMI) has been evaluated in previous clinical trials, the influence of the timing of cell delivery on the effect on left ventricular function has not been analyzed.

OBJECTIVES

To determine the effect of intracoronary autologous bone marrow mononuclear cell (BMC) delivery after STEMI on recovery of global and regional left ventricular function and whether timing of BMC delivery (3 days vs 7 days after reperfusion) influences this effect.

DESIGN, SETTING, AND PATIENTS

A randomized, 2 × 2 factorial, double-blind, placebo-controlled trial, Timing In Myocardial infarction Evaluation (TIME) enrolled 120 patients with left ventricular dysfunction (left ventricular ejection fraction [LVEF] ≤ 45%) after successful primary percutaneous coronary intervention (PCI) of anterior STEMI between July 17, 2008, and November 15, 2011, as part of the Cardiovascular Cell Therapy Research Network sponsored by the National Heart, Lung, and Blood Institute.

INTERVENTIONS

Intracoronary infusion of 150 × 106 BMCs or placebo (randomized 2:1) within 12 hours of aspiration and cell processing administered at day 3 or day 7 (randomized 1:1) after treatment with PCI.

MAIN OUTCOME MEASURES

The primary end points were change in global (LVEF) and regional (wall motion) left ventricular function in infarct and border zones at 6 months measured by cardiac magnetic resonance imaging and change in left ventricular function as affected by timing of treatment on day 3 vs day 7. The secondary end points included major adverse cardiovascular events as well as changes in left ventricular volumes and infarct size.

RESULTS

The mean (SD) patient age was 56.9 (10.9) years and 87.5% of participants were male. At 6 months, there was no significant increase in LVEF for the BMC group (45.2% [95% CI, 42.8% to 47.6%] to 48.3% [95% CI, 45.3% to 51.3%) vs the placebo group (44.5% [95% CI, 41.0% to 48.0%] to 47.8% [95% CI, 43.4% to 52.2%]) (P = .96). There was no significant treatment effect on regional left ventricular function observed in either infarct or border zones. There were no significant differences in change in global left ventricular function for patients treated at day 3 (−0.9% [95% CI, −6.6% to 4.9%], P = .76) or day 7 (1.1% [95% CI, −4.7% to 6.9%], P = .70). The timing of treatment had no significant effect on regional left ventricular function recovery. Major adverse events were rare among all treatment groups.

CONCLUSION

Among patients with STEMI treated with primary PCI, the administration of intracoronary BMCs at either 3 days or 7 days after the event had no significant effect on recovery of global or regional left ventricular function compared with placebo.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00684021.

Effect of transendocardial delivery of autologous bone marrow mononuclear cells on functional capacity, left ventricular function, and perfusion in chronic heart failure: the FOCUS-CCTRN trial

CONTEXT

Previous studies using autologous bone marrow mononuclear cells (BMCs) in patients with ischemic cardiomyopathy have demonstrated safety and suggested efficacy.

OBJECTIVE

To determine if administration of BMCs through transendocardial injections improves myocardial perfusion, reduces left ventricular end-systolic volume (LVESV), or enhances maximal oxygen consumption in patients with coronary artery disease or LV dysfunction, and limiting heart failure or angina.

DESIGN, SETTING, AND PATIENTS

A phase 2 randomized double-blind, placebo-controlled trial of symptomatic patients (New York Heart Association classification II-III or Canadian Cardiovascular Society classification II-IV) with a left ventricular ejection fraction of 45% or less, a perfusion defect by single-photon emission tomography (SPECT), and coronary artery disease not amenable to revascularization who were receiving maximal medical therapy at 5 National Heart, Lung, and Blood Institute-sponsored Cardiovascular Cell Therapy Research Network (CCTRN) sites between April 29, 2009, and April 18, 2011.

INTERVENTION

Bone marrow aspiration (isolation of BMCs using a standardized automated system performed locally) and transendocardial injection of 100 million BMCs or placebo (ratio of 2 for BMC group to 1 for placebo group).

MAIN OUTCOME MEASURES

Co-primary end points assessed at 6 months: changes in LVESV assessed by echocardiography, maximal oxygen consumption, and reversibility on SPECT. Phenotypic and functional analyses of the cell product were performed by the CCTRN biorepository core laboratory.

RESULTS

Of 153 patients who provided consent, a total of 92 (82 men; average age: 63 years) were randomized (n = 61 in BMC group and n = 31 in placebo group). Changes in LVESV index (-0.9 mL/m(2) [95% CI, -6.1 to 4.3]; P = .73), maximal oxygen consumption (1.0 [95% CI, -0.42 to 2.34]; P = .17), and reversible defect (-1.2 [95% CI, -12.50 to 10.12]; P = .84) were not statistically significant. There were no differences found in any of the secondary outcomes, including percent myocardial defect, total defect size, fixed defect size, regional wall motion, and clinical improvement.

CONCLUSION

Among patients with chronic ischemic heart failure, transendocardial injection of autologous BMCs compared with placebo did not improve LVESV, maximal oxygen consumption, or reversibility on SPECT.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00824005.

Effect of intracoronary delivery of autologous bone marrow mononuclear cells 2 to 3 weeks following acute myocardial infarction on left ventricular function: the LateTIME randomized trial

CONTEXT

Clinical trial results suggest that intracoronary delivery of autologous bone marrow mononuclear cells (BMCs) may improve left ventricular (LV) function when administered within the first week following myocardial infarction (MI). However, because a substantial number of patients may not present for early cell delivery, the efficacy of autologous BMC delivery 2 to 3 weeks post-MI warrants investigation.

OBJECTIVE

To determine if intracoronary delivery of autologous BMCs improves global and regional LV function when delivered 2 to 3 weeks following first MI.

DESIGN, SETTING, AND PATIENTS

A randomized, double-blind, placebo-controlled trial (LateTIME) of the National Heart, Lung, and Blood Institute-sponsored Cardiovascular Cell Therapy Research Network of 87 patients with significant LV dysfunction (LV ejection fraction [LVEF] ≤45%) following successful primary percutaneous coronary intervention (PCI) between July 8, 2008, and February 28, 2011.

INTERVENTIONS

Intracoronary infusion of 150 × 10(6) autologous BMCs (total nucleated cells) or placebo (BMC:placebo, 2:1) was performed within 12 hours of bone marrow aspiration after local automated cell processing.

MAIN OUTCOME MEASURES

Changes in global (LVEF) and regional (wall motion) LV function in the infarct and border zone between baseline and 6 months, measured by cardiac magnetic resonance imaging. Secondary end points included changes in LV volumes and infarct size.

RESULTS

A total of 87 patients were randomized (mean [SD] age, 57 [11] years; 83% men). Harvesting, processing, and intracoronary delivery of BMCs in this setting was feasible. Change between baseline and 6 months in the BMC group vs placebo for mean LVEF (48.7% to 49.2% vs 45.3% to 48.8%; between-group mean difference, -3.00; 95% CI, -7.05 to 0.95), wall motion in the infarct zone (6.2 to 6.5 mm vs 4.9 to 5.9 mm; between-group mean difference, -0.70; 95% CI, -2.78 to 1.34), and wall motion in the border zone (16.0 to 16.6 mm vs 16.1 to 19.3 mm; between-group mean difference, -2.60; 95% CI, -6.03 to 0.77) were not statistically significant. No significant change in LV volumes and infarct volumes was observed; both groups decreased by a similar amount at 6 months vs baseline.

CONCLUSION

Among patients with MI and LV dysfunction following reperfusion with PCI, intracoronary infusion of autologous BMCs vs intracoronary placebo infusion, 2 to 3 weeks after PCI, did not improve global or regional function at 6 months.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00684060.

Highly sensitive thromboplastins do not improve INR precision

For determination of the international normalized ratio (INR), it has been suggested that "highly sensitive" thromboplastin reagents (International Sensitivity Index [ISI] < or = 1.2) provide the most consistent performance and minimize interlaboratory variability. We compared the INR values obtained from 69 specimens drawn from patients receiving long-term oral anticoagulant therapy, using four thromboplastin preparations (manufacturer-assigned ISI range of 0.96-1.10) and two automated photo-optical analyzers. Multivariate analysis of the INR response matrix (552 INR values) indicated that the eight reagent-coagulometer combinations did not produce equivalent INR values. Similar analysis indicated that INR values were not normalized when uncorrected prothrombin ratios or INR values, calculated after assignment of "local ISI values" to each thromboplastin reagent, were compared. The INR differences also seemed to be clinically significant because 17% to 29% of paired thromboplastin values were discordant when all INR values were assigned to one of four therapeutic categories used in oral anticoagulant therapy (< 2.0; 2.0-3.0; 3.0-4.5; or > 4.5). These differences in INR values obtained with two photo-optical coagulometers and four highly sensitive thromboplastin reagents suggest that the existing INR system has not achieved the goal of standardized prothrombin time values and does not support the recommendation to use only highly sensitive reagents for the regulation of oral anticoagulant therapy.

Keyhole limpet hemocyanin: structural and functional characterization of two different subunits and multimers

Keyhole limpet hemocyanin (KLH), the large respiratory glycoprotein from the primitive gastropod mollusc, Megathura crenulata, is a potent immunogen used classically as a carrier protein for haptens and more recently in human vaccines and for immunotherapy of bladder cancer. Two KLH isoforms were identified and isolated by high-performance anion exchange chromatography. Subsequent analyses disclosed that these isoforms--designated KLH-A and KLH-B--were composed of distinct subunits that differed in primary structure, molecular weight (KLH-A was 449,000 and KLH-B was 392,000), polymerization/reassociation characteristics, and O2-binding constants (KLH-A had a P50 of 7.32 and KLH-B had a P50 of 2.46). Both subunits appear to be composed of eight oxygen binding domains, and reassociate in solution only with like subunits. These results support the concept that structural and functional heterogeneity is a common feature of molluscan hemocyanins, and provide a rational basis for studying and optimizing the immunostimulatory properties of KLH.

A high-sensitivity thromboplastin reagent prepared from cultured human cells

High-sensitivity thromboplastin reagents suitable for use in the prothrombin time (PT) assay are typically prepared from human brain and placenta, tissues that are in limited supply and subject to viral contamination. Cloning and expression of recombinant human tissue factor (TF) has enabled production of a new generation of thromboplastin reagents whose performance and utility are under active investigation. The purpose of this study was to determine the feasibility of producing a sensitive human thromboplastin reagent from a non-recombinant source: cultured human cells. Several human cell lines with apparently high constitutive TF synthesis were identified, and a viable thromboplastin reagent (Humaplastin) was produced from a human lung cell line via a non-conventional process that did not require reconstitution or rehydration of TF in cell membranes. When calibrated against BCT/253, a human brain international reference thromboplastin, Humaplastin exhibited a mean normal prothrombin time of 12.6 +/- 0.7 s (mean +/- SD: n = 20) and an International Sensitivity Index of 1.09 +/- 0.019. The performance of this reagent was well correlated (r = 0.983) with Thromborel S, a commercially available human placental thromboplastin reagent. Orthogonal least squares regression of the log PT values from the placental thromboplastin reagent versus Humaplastin and two recombinant TF-based thromboplastin reagents suggested that the latter three reagents are somewhat more sensitive than the placental thromboplastin reagent, although such differences should not be expected to have a significant impact on clinical utility. It is concluded that cultured human lung cells represent a suitable source of tissue thromboplastin for production of a high-sensitivity non-recombinant thromboplastin reagent.

Immunotherapy with keyhole limpet hemocyanin: efficacy and safety in the MB-49 intravesical murine bladder tumor model

The antitumor activity and potential toxicity of a clinical-grade keyhole limpet hemocyanin preparation (KLH-Immune Activator; KLH-IA) were determined in the MB-49 intravesical murine bladder tumor model. Mice were immunized subcutaneously with KLH-IA two weeks prior to intravesical implantation of MB-49 tumor cells. Treatment consisted of intravesical KLH-IA (10 or 100 micrograms.) 1, 4, 7, 14 and 21 days after implantation. Control animals either were not immunized prior to tumor implantation and KLH-IA treatment, or were immunized with KLH-IA and treated with the vehicle. By 4 weeks after implantation tumor outgrowth in the treated groups was significantly decreased (p < 0.01, Fisher's Exact) relative to the control groups. Prior subcutaneous immunization was required to elicit antitumor activity of KLH-IA; thus, the mechanism of action is immune-mediated and not due to spurious interference with tumor implantation by intravesical instillations. Animals treated with a dissociated form of KLH exhibited decreased tumor outgrowth approaching, but not attaining, significance (p < 0.09, Fisher's Exact). A separate toxicity study in which KLH-IA was given subcutaneously (4 mg./kg.), intraperitoneally (40 mg./kg.), or intravesically (40 mg./kg.) disclosed no significant gross or histopathologic abnormalities except for mild-to-moderate papillary hyperplasia in all catheterized animals. These results establish the efficacy and safety of KLH-IA in mice and suggest that clinical trials for intravesical treatment of superficial bladder cancer may be warranted.

A comparative evaluation of ELISAs for D-dimer and related fibrin(ogen) degradation products

This study was designed to (i) characterize two new monoclonal antibodies that react with neoepitopes on fibrin(ogen) fragments D-dimer and D1 and (ii) compare the specificity of these antibodies with that of two commercially available 'D-dimer' ELISAs [Dimertest EIA (American Diagnostica, Inc.) and Asserachrom D-Di (Diagnostica Stago)] and also with an ELISA for fibrinolytic fragments containing the E domain complexed with a D (or D-dimer) moiety [Fibrinostika FbDP (Organon Teknika)]. All assays were in a capture (sandwich) ELISA format. Fibrin(ogen) degradation products were isolated in high yield by a novel method involving hydrophobic interaction chromatography. The results disclosed considerable differences in sensitivity and specificity for purified fibrinolytic fragments among all five ELISAs. Although the diagnostic utility of monitoring plasma fibrinolytic fragments is not questioned, our results provide a rational basis for understanding why mAb-based ELISAs for these analytes are not well correlated. If, as our data suggest, the D-dimer ELISAs are not actually measuring the same analytes, then interpretation of studies that determine D-dimer concentrations with different methods will be problematic and standardization of D-dimer measurements across assays will be impossible.

Immunotherapy of murine bladder cancer with keyhole limpet hemocyanin (KLH)

Keyhole limpet hemocyanin (KLH) is a potent immunogen that is being evaluated as an immunotherapeutic alternative to BCG in the treatment of bladder cancer. In the mouse bladder tumor model (MBT2) intralesional KLH significantly reduced tumor incidence, growth rate, and mortality and exhibited antitumor activity similar to that achievable with BCG. Endotoxin contamination of KLH was not responsible for the antitumor activity, although endotoxin alone was shown to have anti-tumor activity in this animal model. Keyhole limpet hemocyanin is both safe and effective in the MBT2 model, and is an immunomodulator to consider for clinical trials.

Immunotoxin construction with a ribosome-inactivating protein from barley

The aim of this study was to determine the suitability of a ribosome-inactivating protein (RIP) from barley endosperm for use as an immunotoxin. This barley RIP is identical with the 30-kDa protein first reported by Coleman and Roberts [(1982) Biochim. Biophys. Acta 696, 239] and sequenced by Asano and co-workers [(1986) Carlsberg Res. Commun. 51, 75]. Use of the terms barley toxin I, II, and III is proposed to describe the three isoforms resolved by cation-exchange chromatography. An improved procedure for isolating the protein involving the steps of aqueous extraction, ammonium sulfate precipitation, and cation-exchange HPLC is described. Barley toxin II retained activity after exposure to ca. 40% acetonitrile and 0.1% trifluoroacetic acid or lyophilization. In a comparative study using the rabbit reticulocyte lysate assay, the protein was about 68% and 30% as potent as gelonin and ricin A-chain (RTA), respectively. Introduction of SH groups with 2-iminothiolane resulted in a substantial loss of activity as the number of thiol groups approached four. Therefore, it was necessary to limit thiolation to an average of one to two SH groups per toxin molecule. Anti-transferrin receptor-based immunotoxins constructed with RTA, gelonin, and barley toxin II exhibited comparable cytotoxicity against a human colon tumor cell line. We conclude that the availability of raw material, ease of purification, and stability of barley toxin II to lyophilization and denaturing conditions render it a suitable protein for the construction of immunotoxins.

Fibrinogen Baltimore IV: congenital dysfibrinogenemia with a gamma 275 (Arg----Cys) substitution

The major functional characteristics of fibrinogen Baltimore IV include delayed fibrin monomer polymerization which is not corrected by the addition of calcium, inhibition of normal plasma coagulation upon mixing, and a biphasic polymerization profile in which the abnormal fibrin monomers appear to polymerize at about 2% of the normal rate (Ebert & Bell, Thromb. Res. 38:121-128, 1985). We now report the detection of an abnormal peptide in a comparative peptide map from a cyanogen bromide digest of fibrinogen Baltimore IV. The sequence of this peptide corresponds to the fibrinogen sequence gamma 265-310, except that Arg275 is replaced by Cys. Amino acid analyses of carboxymethylated peptides from control vs. fibrinogen Baltimore IV confirmed the sequencing data. Both the propositus and his affected daughter were heterozygous for the trait.

Fibrinogen Baltimore III: congenital dysfibrinogenemia with a shortened gamma-subunit

An abnormal fibrinogen has been found in an asymptomatic Negro female. Clinical laboratory findings were normal, except for a prolonged thrombin time which was corrected by addition of calcium. Fibrinopeptide release by thrombin and crosslinking by factor XIII also occurred normally, but fibrin monomer polymerization was delayed. Sodium dodecylsulfate-polyacrylamide gel electrophoresis disclosed that 50% of the gamma-subunits migrated with an apparent Mr of 45,500, approximately 1,500 Da smaller than normal. The evidence suggests that an internal sequence of 10-15 residues is missing from the gamma-subunit of the abnormal fibrinogen.

Isolation and comparative peptide mapping of fibrinogen subunits by reversed-phase high-performance liquid chromatography

Comparative peptide mapping represents one approach to identification of structural defects in variant human fibrinogens. In view of the large size of this protein, we chose to generate peptide maps of fibrinogen subunits. A reversed-phase high-performance liquid chromatographic method was developed to isolate the subunits: fibrinogen was reduced with dithioerythritol and alkylated with iodoacetamide. Subunits were isolated on a Vydac TP, C4 column (25 x 1.0 cm). Eluent A was 0.1% aqueous trifluoroacetic acid (TFA); eluent B was 0.1% TFA in acetonitrile. Initial conditions were 65% A, 35% B, at 2 ml/min. The reduced-alkylated subunits were lyophilized, redissolved in 0.1% TFA plus 4-8 M guanidine-HCl, and chromatographed using a linear gradient (1%/min) to 50% B. This procedure provides homogeneous subunits in yields exceeding 90%, and is therefore superior to conventional cation-exchange chromatography. For comparative peptide mapping, the same stationary and mobile phases were used, except that the initial conditions were 90% A/10% B, and a linear gradient to 60% B (1%/min) was used. Alternatively, peptide maps were generated with a 10 x 0.46 cm Spherisorb ODS-2 column and very shallow gradients. The mapping procedure resolves 45-60 peptides with excellent reproducibility, and has been applied to the identification of an apparent polymorphism in fibrinogen Baltimore II, and the structural defect in fibrinogen Baltimore IV.

The mechanism of action of barley toxin: a type 1 ribosome-inactivating protein with RNA N-glycosidase activity

In a previous report (Endo, Y. and Tsurugi, K. (1987) J. Biol. Chem. 262, 8128-8130) it was shown that the RNA N-glycosidase activity of ricin A-chain was responsible for the ability of this protein to inactivate eukaryotic ribosomes. The objective of the present study was to determine whether a similar mechanism was used by a ribosome-inactivating protein from pearled barley (barley toxin). Rat liver ribosomes were incubated either with ricin A-chain or barley toxin, and the rRNA was extracted and treated with acidic aniline to hydrolyze phosphodiester bonds rendered susceptible by removal of a purine or pyrimidine base. Evaluation of the rRNA by polyacrylamide/agarose electrophoresis disclosed two 28 S rRNA-derived fragments which differed in size from those generated by untreated (control) ribosomes. Sequencing of the smaller of these fragments confirmed that - as is the case for ricin A-chain - the aniline-sensitive site in barley toxin-treated ribosomes was between A and G in 28 S rRNA. We conclude that barley toxin inactivates ribosomes via a mechanism identical to that of ricin A-chain: enzymatic hydrolysis of the N-glycosidic bond at A of 28 S rRNA.

Intracellular growth factors in polycythemia vera and other myeloproliferative disorders

In polycythemia vera, idiopathic myelofibrosis, and essential thrombocytosis, hematopoietic cell proliferation is increased in the absence of a recognizable stimulus, suggesting the autonomous production of growth factors in these disorders. Sonicates of peripheral blood mononuclear cells (PBMNC) from patients with polycythemia vera, idiopathic myelofibrosis, and essential thrombocytosis contained soluble factors that stimulated the proliferation of quiescent-confluent 3T3 cells. PBMNC sonicates from normal individuals; from patients with secondary erythrocytosis, chronic myelogenous leukemia, B-cell chronic lymphocytic leukemia, and acute myelogenous leukemia; and from K-562 and HL-60 cells did not stimulate proliferation. Polycythemia vera PBMNC sonicates also induced anchorage-independent colony formation in soft agar by normal rat kidney fibroblasts. Both the mitogenic and transforming activities of the polycythemia vera PBMNC sonicates resided in the T-lymphocyte-depleted mononuclear fraction of the PBMNC and were not secreted. By gel filtration, reversed-phase HPLC and NaDodSO4/PAGE, the mitogenic and transforming activities in the polycythemia vera PBMNC were localized to three proteins with molecular masses of 13-, 17-, and 65-kDa. The 13-kDa protein was only mitogenic, and the 17-kDa protein was only transforming, whereas the 65-kDa protein had both mitogenic and transforming activity. These proteins may be involved in the autonomous hematopoiesis that characterizes polycythemia vera, idiopathic myelofibrosis, and essential thrombocytosis.

Fibrinogen Seattle II: congenital dysfibrinogenemia with an Arg (A alpha 16)----his substitution

Incubation of fibrinogen Seattle II with thrombin (17 mu/ml) resulted in the release of two forms of fibrinopeptide A (FpA) which were resolved by high-performance liquid chromatography. Amino acid analysis disclosed that the abnormal FpA contained histidine in place of arginine. At lower, approximately physiologic thrombin concentrations only half the normal amount of FpA was released, and fibrinopeptide B (FpB) release was delayed. The effect of this substitution on the time course of fibrinopeptide release is consistent with conclusions drawn from other studies on the kinetics of fibrinopeptide release, viz., that prior removal of FpA is not required before FpB hydrolysis by thrombin, and that optimal rates of FpB release occur after formation of fibrin I polymer.

Amino acid analysis by HPLC: optimized conditions for chromatography of phenylthiocarbamyl derivatives

A method for analysis of phenylthiocarbamyl-amino acids by HPLC is described. Solvent A contains 0.05 M sodium acetate plus triethylamine (2.75 ml/liter) adjusted to pH 6.40 with phosphoric acid. Solvent B consists of 50% solvent A, 40% acetonitrile, and 10% methanol. The stationary phase is a 3-micron Spherisorb ODS-2 column (4.6 X 100 mm). A new sample can be injected every 27 min. Variation of the triethylamine concentration from 1 to 4 ml/liter is shown to affect column selectivity in a predictable manner, and this provides a rational basis for optimizing chromatographic conditions. Resolution of certain hydrophilic amino acids (Arg, Thr, Ala, and Pro), and mobile phase stability are improved over previously described procedures.

Purification and characterization of two isoforms of Acanthamoeba profilin

Acanthamoeba profilin purified according to E. Reichstein and E.D. Korn (1979, J. Biol. Chem. 254:6174-6179) consists of two isoforms (profilin-I and-II) with approximately the same molecular weight and reactivity to a monoclonal antibody but different isoelectric points and different mobilities on carboxymethyl-agarose chromatography and reversed-phase high-performance liquid chromatography. The isoelectric points of profilin-I is approximately 5.5 and that of profilin-II is greater than or equal to 9.0. Tryptic peptides from the two proteins are substantially different, which suggests that there are major differences in their sequences. At similar concentrations, both profilins prolong the lag phase at the outset of spontaneous polymerization and inhibit the extent of polymerization. Both forms also inhibit elongation weakly at the barbed end and strongly at the pointed end of actin filaments.

Localization of a fibrinogen calcium binding site between gamma-subunit positions 311 and 336 by terbium fluorescence

Calcium is required for effective fibrin polymerization. The high affinity Ca2+ binding capacity of fibrinogen was directly localized to the gamma-chain by autoradiography of nitrocellulose membrane blots of fibrinogen subunits incubated with 45Ca2+. Terbium (Tb3+) competitively inhibited 45Ca2+ binding to fibrinogen during equilibrium dialysis, accelerated fibrin polymerization, and limited fibrinogen fragment D digestion by plasmin. The intrinsic fluorescence of Ca2+-depleted fibrinogen was maximally enhanced by Ca2+ and Tb3+, but not by Mg2+, at about 3 mol of cation/mol of fibrinogen. Protein-bound Tb3+ fluorescence at 545 nm was maximally enhanced by resonance energy transfer from tryptophan (excitation at 290 nm) at about 2 mol of Tb3+mol of fibrinogen and about 1 mol of Tb3+/mol of plasmic fragment D94 (Mr 94,000). Fibrinogen fragments D78 (Mr 78,000) and E did not show effective enhancement of Tb3+ fluorescence, suggesting that the Ca2+ site is located within gamma 303 to gamma 411, the peptide which is absent in fragment D78 but present in D94. When CNBr fragments of the carboxyamidated gamma-subunit were assayed for enhancement of Tb3+ fluorescence, peptide CBi (gamma 311-336) bound 1 mol of Tb3+/mol of CBi. Thus, the Ca2+ site is located within this peptide. The sequence between gamma 315 and gamma 329 is homologous to the calmodulin and parvalbumin Ca2+ binding sites.

Assay of human fibrinopeptides by high-performance liquid chromatography

Fibrinopeptides A, AP, and B, desarginine fibrinopeptide B, and a previously unknown peptide corresponding to B beta 3-14 were resolved within 10 min by an HPLC technique using an isocratic solvent system (22% acetonitrile in 0.1% trifluoroacetic acid) and a 0.46 X 10-cm Spherisorb ODS-2 (3-micron) octadecylsilane column. Fibrinopeptides A and AY eluted in the same peptide peak. The method was used to evaluate a carboxypeptidase which converts fibrinopeptide B into its desarginine form. Fifty percent inhibition of this activity occurred at 1.7 mM epsilon-aminocaproic acid (EACA). At saturating substrate concentrations the rates of total fibrinopeptides A and B release were unaffected by 125 mM EACA, a concentration at which the carboxypeptidase activity is completely inhibited.

Protective effect of divalent cations in the plasmin degradation of fibrinogen

Calcium limits the plasmic proteolysis of fibrinogen fragment D by binding to a specific site on the carboxy-terminal segment of the D gamma chain. Employing sodium dodecyl sulfate-polyacrylamide gel electrophoresis to visualize plasmic fragments, Sr2+, Ba2+, and Mn2+ were found to have an equivalent capacity to limit the degradation of fibrinogen fragment D (Mr 94,000). Mg2+, Fe2+, Co2+, and Zn2+ did not comparably limit the digestion of fragment D. Equilibrium dialysis demonstrated that Ba2+ competitively inhibited Ca2+ binding to fibrinogen, suggesting that the ions occupied the Ca2+ binding site of fibrinogen and thereby limited the plasmic digestion of fragment D. The results suggest that Ca2+, Sr2+, Ba2+, and Mn2+ limit plasmin digestion of fragment D by interacting with a Ca2+ binding site in the D domain of the fibrinogen molecule.

Fibrinogen Baltimore IV: congenital dysfibrinogenemia with delayed fibrin monomer polymerization

A congenital dysfibrinogenemia, fibrinogen Baltimore IV, has been found in a 56-year-old Caucasian man. Clinical laboratory studies disclosed a slightly prolonged prothrombin time, but were otherwise unremarkable. Release of fibrinopeptides by thrombin occurs normally, as does ligation of the fibrin polymer by Factor XIII. Approximately half of the isolated fibrin monomers polymerize normally, but the remainder polymerize at about 2% of the initial rate. The functional defect is thus limited to a decrease in the rate of fibrin monomer polymerization.

Fibrinogen Baltimore II: congenital hypodysfibrinogenemia with delayed release of fibrinopeptide B and decreased rate of fibrinogen synthesis

A congenital hypodysfibrinogenemia, fibrinogen Baltimore II, was found in a young asymptomatic Caucasian female. Prothrombin, partial thromboplastin, and euglobulin lysis times were normal, as were platelet function and coagulation factor assays. Subnormal plasma fibrinogen levels were found using chronometric, rate-independent, and immunologic assay methods. Kinetic analysis of fibrinopeptide release revealed a delay in the thrombin-catalyzed release of fibrinopeptide B from the abnormal protein. Proteolysis of fibrinopeptide A by thrombin or Arvin, fibrin monomer polymerization, and fibrin polymer ligation occurred at normal rates. Catabolism of radiolabeled autologous and homologous fibrinogen was also normal, but the fibrinogen synthetic rate was less than half the normal value. Comparison of the coagulation characteristics of fibrinogen Baltimore II with those of other abnormal fibrinogens indicates that it represents a unique example of hypodysfibrinogenemia.

Isolation and characterization of two adenosine 3',5'-monophosphate-dependent protein kinases from bovine adrenal cortex

Bovine adrenocortical cytosol contains two cAMP-dependent protein kinases separable by diethylamino-ethyl-cellulose chromatography. The kinases exhibit behavior characteristic of type I and type II enzymes i.e. the enzyme eluting at 80 mM NaCl is activated by NaCl and histone, whereas the enzyme eluting at 140 mM NaCl is not. In addition, a third cAMP-binding protein eluting from DEAE at 120 mM NaCl has been isolated and tentatively identified as type I regulatory subunit. A method is described for the isolation of the catalytic and regulatory subunits of both enzymes from the same starting material using cGMP to dissociate the enzyme subunits and elute the regulatory subunits from N6-aminoethyl-cAMP-Sepharose 4B. The isolated proteins were homogeneous, as judged by sodium dodecyl sulfate-polyacrylamide electrophoresis. Using this technique, molecular weight values of 44,000 for the catalytic subunits, 51,000 for the cAMP-binding protein and type I regulatory subunit, and 56,000 for the type II regulatory subunit were obtained. Molecular weights obtained by sucrose density gradient centrifugation on the cGMP-dissociated holoenzymes were 95,000 and 101,000 for regulatory subunits from type I and II enzymes and 34,000 and 33,000 for their respective catalytic subunits. The apparent Km and Vmax values for catalytic subunits I and II were similar when histone, casein, or ATP was used as substrate. The Vmax for protamine phosphorylation was 3-fold higher with catalytic subunit II. Phosvitin was not a substrate for either subunit. The cAMP-binding protein and regulatory subunit I were able to recombine with, i.e. inhibit, either catalytic subunit. At a molar ratio of 4:1, inhibition was total. The type II regulatory subunit was considerably less effective. Preference for a particular catalytic subunit was not evident in the case of inhibition by either regulatory subunit or the cAMP-binding protein.